Many forms of boat and like covers are known, some of which are simple, make-shift canvas or like covers and others of which are button-on, button-off types. Others may be manually rolled and unrolled. All these have various use and operational disadvantages, especially when attempted to be installed in windy conditions. According to the present invention, these disadvantages are eliminated by the provision of a cover construction that is compact and simple, that is easily attached to a boat and that is substantially foolproof in use and operation. The invention features guides or channels having means for the affixation thereof respectively to the fore-and-aft edges of the cockpit sides. The cover sheet is wound or wrapped on a powered roller that spans the guides and is suitably housed in a casing readily attachable to the transom of the cockpit. Improved control means is provided for effecting rolling and unrolling of the cover, including actuating means for starting and stopping the roller manually and for automatically stopping the unrolling operation when the cover has reached its intended covering status.